1. Field of the Invention
This invention relates generally to heat welding of thermoplastics and more particularly to hot gas welding of two or more thermoplastic components.
2. Description of the Prior Art
In a conventional method of hot gas welding, a welding gun is held in one hand and a filler rod, made of the same material as the parts to be welded, is held in the other hand.
With the method of such hand welding, a high degree of operator's skill and judgment are required. In addition, the hand welding of the above type must be carried out in a continuous manner from one end to the other end of the weld, with the parts clamped and positioned in each fixture. The hot gas stream must be directed in a fanning motion back and forth between the two sides of the joint as well as onto the approaching filler rod. Since the strength of the weld is greatly affected by the uniformity of pressure exerted by the rod into the joint, experience and care are required for a successful welding.
Such hand welding cannot be applied in the automobile industry which adopts a mass production system.
In another method of heat welding, a very popular contact heat weld has been used in a high-speed automatic process. In this method, a heat plate is disposed between the parts to be welded and the two parts are pressurized against the heat plate for a short period of time. Then the fixtures or clamps are retracted and the heat plate is also withdrawn, and finally the parts are pressed together under a controlled pressure to join the two parts.
This method, however, has a significant problem as to the prevention of sticking of the melted parts to the heat plate.